Field of the Invention
The present invention relates to a servomotor control device and servomotor control system which have a self-monitoring function for aging in the rigidity of a connection mechanism that connects a servomotor and driven body and transmits drive power of the servomotor to the driven body.
Related Art
For example, a servomotor control device has been known that controls the position of a workpiece (work) using servomotors in a machine tool or the like. The servomotor control device mounts the workpiece on a table (driven body) (also referred to as mobile body), and causes the table to move by a servomotor via the connection mechanism. The connection mechanism has a coupling connected to a servomotor, a ball screw that is fixed to the coupling, and a nut that is threaded with the ball screw, and connected to the table. When causing the ball screw to rotate by way of the servomotor, the nut threaded to the ball screw is driven in the axial direction of the ball screw, and the table connected to the nut is thereby moved.
With such a connection mechanism (particularly the coupling and ball screw), the rigidity is relatively low, and elastic deformation occurs. When the connection mechanism elastically deforms, error in the amount of elastic deformation arises in the position of the table. Concerning this point, technology for correcting the position of the table has been known.
Patent Documents 1 and 2 disclose technology for correcting positional error (positioning error) caused by aging of rigidity of the connection mechanism, based on the rotation amount of the servomotor detected by an encoder in the servomotor (semi-closed feedback value), and a movement amount of the table detected by a linear scale fixed to the table (full-closed feedback value).
Patent Document 1: Japanese Unexamined Patent Application, Publication No. H11-345025
Patent Document 2: Japanese Unexamined Patent Application, Publication No. H11-237920